Workpiece bending method and workpiece bending apparatus

ABSTRACT

workpiece bending method and a workpiece bending apparatus that allow setting of a trajectory of a bending implement based upon a pre-processed shape of a workpiece and an intended post-processed shape of the workpiece. The workpiece bending method bends a flange of a workpiece via a processing roller, and includes a step for obtaining a pre-processed angle of the flange before processing and a flange length of the portion of the flange to be bent; a trajectory determination step for determining a path (trajectory) of the processing roller based upon the pre-processed angle, an intended angle after processing, and the flange length; and a processing step for moving the processing roller in a prescribed direction in accordance with the path determined in the trajectory determination step and then bending the flange until the intended angle is achieved.

TECHNICAL FIELD

The present invention relates to a technique for performing a bending process on an end portion of a workpiece with a processing tool.

BACKGROUND ART

From related art, there has been known a technique of moving a processing tool such as a hemming roller against an end portion of a plate material to perform a bending process on the end portion of the plate material. For example, Patent Document 1 discloses such a kind of technique. Patent Document 1 discloses a technique for learning an angle change operation and the like of a preliminary bending and a main bending in a hemming apparatus which performs the bending process with a hemming roller.

Patent Document 1: Japanese Unexamined Patent Application, Publication No. H2-197331

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

A trajectory of the processing tool for performing the bending process on the workpiece also varies not only by the shape of the workpiece but also the state of the workpiece before bending process and the state of the workpiece after bending up to an intended angle. Since the trajectory of the processing tool is set by experiences of experienced technicians or the like, it takes time to perform a teaching operation of the processing apparatus at the site depending on the worker. In this regard, also in the technique disclosed in Patent Literature 1 which is learned beforehand, it is required to learn the state of the workpiece before performing the bending process and the state of the workpiece after the bending up to the intended angle in consideration of the trajectory of the processing tool, and there is room for improvement from the viewpoint of efficiency and reproducibility.

An object of the present invention is to provide a workpiece bending method and a workpiece bending apparatus capable of appropriately setting the trajectory of a processing tool, on the basis of the shape of a workpiece before processing and an intended shape of the workpiece after processing.

Means for Solving the Problems

The present invention relates to a workpiece bending method for performing a bending process on an end portion (for example, a flange WF to be described later) of a workpiece (for example, a workpiece W to be described later) by a processing tool (for example, a processing roller 10 to be described later), the method including: a step of obtaining a pre-processed angle (for example, a pre-processed angle θ₀ to be described later) of the end portion before processing and an end portion length (for example, a flange length L to be described later) of a bent portion of the end portion; a trajectory determination step of determining a trajectory (for example, a path to be described later) of the processing tool on the basis of the pre-processed angle, an intended angle (for example, an intended angle Ψ to be described later) after processing, and the end portion length; and a processing step of moving the processing tool in a predetermined direction on the basis of the trajectory determined in the trajectory determination step and bending the end portion up to the intended angle.

As a result, since the trajectory of the processing tool can be appropriately determined on the basis of the pre-processed angle and the intended angle, it is possible to effectively reduce the number of steps required for setting the trajectory of the processing tool in the teaching operation. Even when the worker has little experience, since an appropriate trajectory is set, the processing process can be stabilized.

In the trajectory determination step, a difference (for example, θ₀−Ψ to be described later) between the pre-processed angle and the intended angle or a value (for example, (θ₀−Ψ)/L to be described later) obtained by dividing the difference by the end portion length or both are preferably calculated as a trajectory determination value, and the number of times of bending (for example, the number of paths to be described later) and the bending angle (for example, a processing intermediate angle θn to be described later) of each step are preferably calculated, from a trajectory number determination map (for example, a trajectory determination map illustrated in FIG. 8 to be described later) in which the trajectory number representing the number of times of bending to be bent in stages from the pre-processed angle to the intended angle is determined in stages depending on the magnitude of the trajectory determination value, and from the calculated trajectory determination value.

Thus, it is possible to automatically and appropriately calculate the number of times of bending by reflecting the processing difficulty level on the basis of the difference between the pre-processed angle and the intended angle.

When the shape of the end portion of the workpiece (for example, a workpiece Wb to be described later) is different in the movement direction of the processing tool, in the trajectory determination step, the trajectory of the processing tool is preferably determined, on the basis of the pre-processed angle, the intended angle, and the end portion length of a first cross section (see No. 1 of FIG. 12) of the end portion viewed in the movement direction of the processing tool, and on the basis of the pre-processed angle, the intended angle, and the end portion length of a second cross section (see Nos. 2 to 15 of FIG. 12) different from the first cross section of the end portion viewed in the movement direction of the processing tool.

Thus, even when the cross-sectional shape is different, the trajectory of the processing tool can be determined in consideration of the difference in shape.

A difference (for example, θ₀−Ψ to be described later) between the pre-processed angle and the intended angle of the first cross section, a value (for example, (θ₀−Ψ)/L to be described later) obtained by dividing the difference by the end portion length or both are preferably calculated as a first trajectory determination value, a difference (for example, θ₀−Ψ to be described later) between the pre-processed angle and the intended angle of the second cross section, a value (for example, (θ₀−Ψ)/L to be described later) obtained by dividing the difference by the end portion length or both are preferably calculated as a second trajectory determination value and the number of times of bending and the bending angle of each step are preferably calculated, from a trajectory number determination map (a trajectory number determination map illustrated in FIG. 13) in which the trajectory number representing the number of times of bending to be bent in stages from the pre-processed angle to the intended angle is determined in stages depending on the magnitude of the trajectory determination value, and from the calculated first and second trajectory determination values.

As a result, even when the cross section varies in the movement direction, the number of times of bending can be automatically and appropriately calculated, by reflecting the processing difficulty level.

In the trajectory number determination map, values for determining an upper limit value (for example, 7.0 in 1 path, 12.0 in 2 paths, or 19.0 in 3 paths in a trajectory number determination map to be described later) for each trajectory number are preferably determined, and the bending angle is preferably calculated in each step by reflecting a deviation (for example, a margin Mα or a margin Mβ to be described later) with respect to the upper limit value in the range (for example, a range of 1 path, a range of 2 paths, or a range of 3 paths to be described later) to which the trajectory determination value plotted in the trajectory number determination map belongs.

As a result, it is possible to appropriately average the processing difficulty level in a case where the cross-sectional shape is different, and to more stably perform the bending process of the workpiece.

Further, the present invention relates to a workpiece bending apparatus (for example, a roller hemming apparatus 1 to be described later) which performs a bending process on an end portion (for example, a flange WF to be described later) of a workpiece (for example, a workpiece W to be described later) by a processing tool (for example, a processing roller 10 to be described later), the apparatus including: a control unit (for example, a control unit 50 to be described later) which obtains a pre-processed angle (for example, a pre-processed angle θ₀ to be described later) of the end portion before processing and an end portion length (for example, a flange length L to be described later) of a bent portion of the end portion, and determines a trajectory (for example, a path to be described later) of the processing tool, on the basis of the pre-processed angle, an intended angle (for example, an intended angle Ψ to be described later) after processing, and the end portion length; and a robot (for example, a robot 40 to be described later) which moves the processing tool in a predetermined direction on the basis of the trajectory determined in the control unit, and bends the end portion up to the intended angle.

Thus, since the trajectory of the processing tool can be appropriately determined on the basis of the pre-processed angle and the intended angle, it is possible to effectively reduce the number of steps required for setting the trajectory of the processing tool in the teaching operation. Even when the experience of the worker is small, since an appropriate trajectory is set, the processing process can be stabilized.

The control unit preferably calculates a difference (for example, θ₀−Ψ to be described later) between the pre-processed angle and the intended angle or a value (for example, (θ₀−Ψ)/L to be described later) obtained by dividing the difference by the end portion length or both, as a trajectory determination value, and the number of times of bending (for example, the number of path to be described later) and the bending angle (for example, a processing intermediate angle θn to be described later) of each step are preferably calculated, from a trajectory number determination map (for example, the trajectory number determination map illustrated in FIG. 6 to be described later) in which the trajectory number representing the number of times of bending to be bent in stages from the pre-processed angle to the intended angle is determined in stages depending on the magnitude of the trajectory determination value, and from the calculated trajectory determination value.

Thus, it is possible to automatically and appropriately calculate the number of times of bending, by reflecting the processing difficulty level on the basis of the difference between the pre-processed angle and the intended angle.

When the shape of the end portion of the workpiece (for example, a workpiece Wb to be described later) is different in the movement direction of the processing tool, in the trajectory determination step, the control unit preferably determines the trajectory of the processing tool, on the basis of the pre-processed angle, the intended angle, and the end portion length of the first cross section of the end portion viewed in the movement direction of the processing tool, and on the basis of the pre-processed angle, the intended angle, and the end portion length of the second cross section different from the first cross section of the end portion viewed in the movement direction of the processing tool.

Thus, even when the cross-sectional shape is different, the trajectory of the processing tool can be determined in consideration of the difference in shape.

A difference (for example, θ₀−Ψ to be described later) between the pre-processed angle and the intended angle of the first cross section, a value (for example, (θ₀−Ψ)/L to be described later) by dividing the difference by the end portion length or both are preferably calculated as a first trajectory determination value, a difference (for example, θ₀−Ψ to be described later) between the pre-processed angle and the intended angle of the second cross section or a value (for example, (θ₀−Ψ)/L to be described later) obtained by dividing the difference by the end portion length or both are preferably calculated as a second trajectory determination value and the number of times of bending and the bending angle of each step are preferably calculated, from a trajectory number determination map (a trajectory number determination map illustrated in FIG. 13) in which the trajectory number representing the number of times of bending to be bent in stages from the pre-processed angle to the intended angle is determined in stages depending on the magnitude of the trajectory determination value, and from the calculated first and second trajectory determination values.

As a result, even when the cross section varies in the movement direction, the number of times of bending can be automatically and appropriately calculated by reflecting the processing difficulty level.

In the trajectory number determination map, values for determining an upper limit value (for example, 7.0 in 1 path, 12.0 in 2 paths, or 19.0 in 3 paths in a trajectory number determination map to be described later) for each trajectory number are preferably determined, and the bending angle is preferably calculated in each step by reflecting a deviation (for example, a margin Mα or a margin Mβ to be described later) with respect to the upper limit value in the range (for example, a range of 1 path, a range of 2 paths, or a range of 3 paths to be described later) to which the trajectory determination value plotted in the trajectory number determination map belongs.

As a result, it is possible to appropriately average the processing difficulty level in a case where the cross-sectional shape is different, and to more stably perform the bending process of the workpiece.

Effects of the Invention

According to the present invention, it is possible to provide a workpiece bending method and a workpiece bending apparatus capable of appropriately setting the trajectory of a processing tool, on the basis of the shape of a workpiece before processing and an intended shape of the workpiece after processing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating a schematic configuration of a roller hemming apparatus 1 according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view schematically illustrating a state in which an outer panel W1 and an inner panel W2 before the preliminary process of the present embodiment are placed on a table section 32.

FIG. 3 is a cross-sectional view illustrating the outer panel W1 and the inner panel W2 in a state in which a flange WF is bent up to the intended angle Ψ by a processing roller 10 in the preliminary process of the present embodiment.

FIG. 4 is a cross-sectional view illustrating the outer panel W1 and the inner panel W2 which are bent into a predetermined shape in a main process of this embodiment.

FIG. 5 is a cross-sectional perspective view illustrating an example of a workpiece Wa having the same cross-sectional shape in a movement direction of the processing roller 10.

FIG. 6 is a flowchart illustrating the flow of movement control of the processing roller 10 in a case where the cross-sectional shape of the workpiece W is the same in the movement direction of the processing roller 10.

FIG. 7 is a diagram describing a difference in the number of paths of the processing roller 10 depending on the processing difficulty level.

FIG. 8 is a diagram illustrating a trajectory number determination map for determining the number of paths of the processing roller 10 in a case where the cross-sectional shape of the workpiece W is the same in the movement direction of the processing roller 10.

FIG. 9 is a diagram describing a difference in movement control of the processing roller 10 depending on the flange length L.

FIG. 10 is a cross-sectional perspective view illustrating an example of a workpiece Wb having different cross-sectional shapes in the movement direction of the processing roller 10.

FIG. 11 is a flowchart illustrating the flow of movement control of the processing roller 10 in a case where the cross-sectional shape of the workpiece W is different in the movement direction of the processing roller 10.

FIG. 12 is a table illustrating a relation between a cross-section of a plurality of places acquired in a range in which a preliminary process is performed and a processing difficulty level.

FIG. 13 is a diagram illustrating a trajectory number determination map for determining the number of paths of the processing roller 10 in a case where the cross-sectional shape of the workpiece W is different in the movement direction of the processing roller 10.

PREFERRED MODE FOR CARRYING OUT THE INVENTION

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. First, an overall configuration of a roller hemming apparatus 1 to which the plate material processing method of the present embodiment is applied will be described. FIG. 1 is a diagram illustrating a schematic configuration of the roller hemming apparatus 1 according to an embodiment of the present invention.

As illustrated in FIG. 1, the roller hemming apparatus 1 of the present embodiment includes a processing table 30, a processing roller 10, a robot 40, and a control unit 50.

The processing table 30 includes a support table 31 installed on a floor surface, and a table section 32 supported by the support table 31. A workpiece W is placed on the table section 32. The workpiece W is, for example, a door panel for a vehicle, and is configured to include an outer panel W1 and an inner panel W2. In the outer panel W1, the flange WF is bent at approximately 90° in a remaining peripheral edge portion with respect to a portion (main body) in which the inner panel W2 is disposed at the center.

In the table section 32, the outer panel W1 is placed in a state in which the flange WF stands upward perpendicular to the surface of the table section 32. On the outer panel W1, the inner panel W2 is disposed so that the flange WF of the outer panel W1 wraps the end portion of the inner panel W2. An adhesive is applied between the main body of the outer panel W1 and the end portion of the inner panel W2 or to a folded-back surface of the flange WF. The adhesive contains a solid material such as glass beads.

The processing roller 10 performs a bending process (a roller hemming process) on the flange WF of the outer panel W1 placed on the table section 32. The processing roller 10 is supported so as to be movable in a three-dimensional direction by an arm 42 of the robot 40, and is rotatable with respect to the arm 42.

The robot 40 includes a base section 41 fixed to the floor surface, and an arm 42 that supports the processing roller 10 so as to be movable in a three-dimensional direction. The robot 40 moves the arm 42 so that the processing roller 10 moves along a predetermined trajectory.

Next, the flow of the bending process performed by the roller hemming apparatus 1 will be described. In the bending process of the present embodiment, a preliminary process of bending the flange WF of the outer panel W1 in stages up to the intended angle Ψ, and a main process of caulking the flange WF bent up to the intended angle Ψ into a final bent shape, are performed.

FIG. 2 is a cross-sectional view schematically illustrating a state in which the outer panel W1 and the inner panel W2 are placed on the table section 32 before performing the preliminary process. In FIG. 2, the vicinity of the flange WF of the outer panel W1 is illustrated.

As illustrated in FIG. 2, the outer panel W1 is placed on the surface of the table section 32 in a state in which the flange WF positioned at the end portion thereof is bent upward. Further, reference numeral R1 in the drawing represents a starting end portion of an R-shaped portion which is the bent portion of the flange WF, and reference numeral R2 represents a terminal end portion of the R-shaped portion. Further, reference numeral L represents a flange length from R2 to the end portion of the outer panel W1. Next, the inner panel W2 is superimposed on the central portion (main body) of the outer panel W1. The end portion of the inner panel W2 is housed inside the flange WF of the main body of the outer panel W1. When a thickness of the outer panel W1 is set as T₁ and a thickness of the inner panel W2 is set as T₂, the thickness obtained by superimposing the outer panel W1 and the inner panel W2 at this time can be expressed as (T₁+T₂).

FIG. 3 is a cross-sectional view illustrating the outer panel W1 and the inner panel W2 in a state in which the flange WF is bent up to the intended angle Ψ by the processing roller 10 in the preliminary process.

As illustrated in FIG. 3, the processing roller 10 of the present embodiment has a substantially cylindrical shape rotatable around a rotation axis C1, and its processed surface has a circumference-shaped section 11 and an R-shaped section 12. A boundary section 13 is formed between the circumference-shaped section 11 and the R-shaped section 12. The circumference-shaped section 11 is provided on the support side of the arm 42 of the robot 40 in the processing roller 10, and the R-shaped section 12 is provided on a tip side which is an opposite side to the support side of the arm 42 of the robot 40 in the processing roller 10. Further, reference numeral 1 in FIG. 3 represents a length in the horizontal direction from the R-shaped starting end portion R1 of the outer panel W1 to the reference position of the processing roller 10. Reference numeral D represents the length in the horizontal direction from the reference position to a processing position at which the processing roller 10 comes into contact with the flange WF, and represents a pushing amount of the processing roller 10. Symbol Ψ is an intended angle Ψ for performing a caulking process.

The robot 40 performs preliminary bending in accordance with a preset trajectory. In the preliminary process of the present embodiment, the preliminary bending is performed in stages a plurality of times.

In the present embodiment, the height of the processing roller 10 is constant, and a processing intermediate angle θn (=1, 2, 3 . . . ) changed once is adjusted by a change in the pushing amount D. A method for setting the number of times of preliminary bending and one preliminary bending angle will be described later.

The pressing of the processing roller 10 against the flange WF is performed by moving the processing roller 10 with respect to the flange WF along a path in which the arm 42 is set to be parallel to the surface of the table section 32.

The caulking process of this step is performed on the flanges WF bent up to the intended angle Ψ. FIG. 4 is a cross-sectional view illustrating the outer panel W1 and the inner panel W2 which are bent into a predetermined shape in the present step of this embodiment.

In this step, the flange WF is bent until it comes into contact with the end portion of the inner panel W2, and the end portion of the inner panel W2 is in a state of being sandwiched between the flange WF and the main body of the outer panel W1. In the present embodiment, the adhesive is applied between the main body of the outer panel W1 and the end portion of the inner panel W2, the folded-back surface of the flange WF or both, and the solid material contained in the adhesive enters between the outer panel W1 and the inner panel W2 to strongly couple the outer panel W1 and the inner panel W2. A thickness h obtained by superimposing the outer panel W1 on the inner panel W2 can be expressed as (2T₁+T₂). In this way, in the caulking process, the flange WF bent up to the intended angle Ψ by the preliminary process is further pushed in, and a state in which the inner panel W2 is sandwiched by the outer panel W1 is obtained.

Next, a method for setting the number of times of processing and the processing angle in the preliminary process will be described. In the roller hemming apparatus 1 of the present embodiment, when the cross-sectional shape of the workpiece W is the same in the movement direction of the processing roller 10, or when the cross-sectional shape of the workpiece W is different in the movement direction of the processing roller 10, the number of times of processing and the processing angle are set by the different calculation methods, and the movement control of the processing roller 10 is performed.

First, a case where the cross-sectional shape of the workpiece W is the same in the movement direction of the processing roller 10 will be described. FIG. 5 is a cross-sectional perspective view illustrating an example of a workpiece Wa (a workpiece W) having the same cross-sectional shape in the movement direction of the processing roller 10. FIG. 6 is a flowchart illustrating the flow of the movement control of the processing roller 10 when the cross-sectional shape of the workpiece W is the same in the movement direction of the processing roller 10. FIG. 7 is a diagram illustrating a difference in the number of paths of the processing roller 10 depending on the processing difficulty level. FIG. 8 is a diagram illustrating a trajectory number determination map for determining the number of paths of the processing roller 10 when the cross-sectional shape of the workpiece W is the same in the movement direction of the processing roller 10. FIG. 9 is a diagram illustrating a difference in movement control of the processing roller 10 depending on the flange length L.

The workpiece Wa illustrated in FIG. 5 is a portion corresponding to a side sill of a vehicle door, and the flange WF of the end portion of the workpiece W is placed on the table section 32 in a state of being bent at a predetermined flange length L and a predetermined angle (hereinafter referred to as a pre-processed angle θ₀).

As illustrated in FIG. 6, the control unit 50 of the roller hemming apparatus 1 acquires the flange length L and the pre-processed angle θ₀ in the flow of the movement control of the processing roller 10 (S101). In the present embodiment, the flange length L and the pre-processed angle θ₀ are set on the basis of preset data such as design data which is set in the previous process.

On the basis of the preset intended angle Ψ before caulking process and the flange length L and the pre-processed angle θ₀ acquired in S101, values for analyzing the processing difficulty level are calculated from Formulas 1 and 2 (S102).

(θ₀−Ψ)/L   Formula 1

θ₀−Ψ  Formula 2

The processing difficulty level will be described with reference to FIG. 7. (a) of FIG. 7 schematically illustrates an example of the workpiece W when the pre-processed angle θ₀ is relatively large, and (b) of FIG. 7 schematically illustrates the workpiece W when the pre-processed angle θ₀ is relatively small. Further, θ₃ of (a) of FIG. 7 and θ₂ of (b) of FIG. 7 are intended angles for performing the caulking process and are assumed to be substantially the same angle.

When the pre-processed angle θ₀ is large and the processing difficulty level is high, the number of paths is set to be large, and when the pre-processed angle θ₀ is small and the processing difficulty level is low, the number of paths is set to be small. For example, in (a) of FIG. 7 in which the pre-processed angle θ₀ is large, the preliminary process is performed three separate times, and in (b) of FIG. 7 in which the pre-processed angle θ₀ is small, the preliminary process is performed two separate times.

As illustrated in FIG. 8, the range for determining the number of paths on the basis of the value of (θ₀−Ψ)/L calculated in S102, and the range for determining the number of paths on the basis of the value of (θ₀−Ψ) are set in advance, respectively.

In the present embodiment, the range for determining the number of paths on the basis of the value of (θ₀−Ψ)/L is 1 path when the value of (θ₀−Ψ)/L is less than 7.0, the range is 2 paths when the value of (θ₀−Ψ)/L is 7.0 or more and less than 12.0, and the range is 3 paths when the value of (θ₀−Ψ)/L is 12.0 or more. On the other hand, the range for determining the number of paths on the basis of the value of θ₀−Ψ is 1 path when the value of θ₀−Ψ is less than 10 deg, the range is 2 paths when the value of θ₀−Ψ is 10 deg or more and less than 60 degrees, and the range is 3 paths when the value of θ₀−Ψ is 60 deg or more.

In the step of determining the number of paths, the number of paths is calculated on the basis of the value calculated by (θ₀−Ψ)/L Formula 1, and the number of paths is calculated on the basis of the value calculated by θ₀−Ψ Formula 2. Further, by comparing the number of paths based on the value of (θ₀−Ψ)/L Formula 1 with the number of paths based on the value of θ₀−Ψ Formula 2, the value with higher processing difficulty level is determined as the number of paths in the preliminary process.

The determination of the number of paths will be described by assigning specific numerical values to Formulas 1 and 2. When the workpiece W of a processing target illustrated in FIG. 5 has a pre-processed angle θ₀=98.17 deg, a flange length L=7.57 (mm), and an intended angle Ψ=30 deg, the following results are obtained.

(θ₀−Ψ)/L=9.00

θ₀−Ψ=68.17

(θ₀−Ψ)/L=9.00 is in the range of 7.0 or more and less than 12.0 in which 2 paths are set, and the number of paths is 2. Since θ₀−Ψ=68.17 deg is equal to or greater than 60 deg in which 3 paths are set, the number of paths is 3. Since the one with higher processing difficulty level is preferred, in this case, the number of paths is set to 3.

When the number of paths is determined, a processing intermediate angle θn set for each path is calculated (S104). When the cross-sectional shape of the workpiece W is the same in the movement direction of the processing roller 10, the processing intermediate angle θn is set as an angle obtained by dividing the angle, which is obtained by subtracting the intended angle Ψ from the pre-processed angle θ0, by the number of paths. In the above example, θ0=98.17 deg, θ1=75.4 deg, θ2=52.7 deg, and θ3=30 deg (=intended angle Ψ) are set as the processing intermediate angle θn.

Next, an intermediate cross section is formed on a CAD on the basis of θ0 (S105), and a pushing amount D1→n of the processing roller 10 is calculated on the basis of this intermediate section (S106).

In the present embodiment, the bending process is performed without changing the height of the processing roller 10. A difference in the movement control of the processing roller 10 depending on the flange length L will be described with reference to FIG. 9.

(a) of FIG. 9 illustrates a case where the flange length L is relatively long, and (b) of FIG. 9 illustrates a case where the flange length L is relatively short.

As illustrated in (a) of FIG. 9, when the flange length L is relatively long, the R-shaped section 12 of the processing roller 10 is brought into surface-contact with the outer surface of the flange WF. As illustrated in (b) of FIG. 9, when the flange length L is relatively short, the circumference-shaped section 11 of the processing roller 10 is brought into line-contact with the end surface of the flange WF.

The pushing amount D, which is set for each path, is set for each processing intermediate angle which is set in each path. For example, in the above example in which θ0=98.17 deg, θ1=75.4 deg, θ2=52.7 deg, and θ3=30 deg are set, the pushing amount D1=4.6 mm is set in the first bending process, the pushing amount D2=7.8 mm is set in the second bending process, and the pushing amount D3=10.4 mm is set in the third bending process.

When the pushing amount is set for each path, the position of the processing roller 10 of the roller hemming apparatus 1 is controlled by the arm 42 of the robot 40, and an actual bending operation is performed. The roller hemming apparatus 1 performs a caulking process on the workpiece W bent up to the intended angle Ψ in the preliminary process.

According to the workpiece bending method and the roller hemming apparatus 1 of the embodiment described above, the following effects are obtained. A workpiece bending method for performing a bending process on a flange WF of a workpiece Wa by a processing roller 10 includes a step of obtaining a pre-processed angle θ₀ of the flange WF before processing and a flange length L of a bent portion of the flange WF; a trajectory determination step of determining a path (trajectory) of the processing roller 10 on the basis of the pre-processed angle θ₀, an intended angle Ψ after processing, and the flange length L; and a processing step of moving the processing roller 10 in a predetermined direction on the basis of the path determined in the trajectory determination step and bending the flange WF up to the intended angle Ψ.

Thus, since the path of the processing roller 10 can be appropriately determined on the basis of the pre-processed angle θ₀ and the intended angle Ψ, it is possible to effectively reduce the number of steps required for setting the path of the processing roller 10 in the teaching operation. Even when the experience of the worker is small, since an appropriate trajectory is set, the processing process can be stabilized.

In the trajectory determination step, both the difference (θ₀−Ψ) between the pre-processed angle θ₀ and the intended angle Ψ and the value ((θ₀−Ψ)/L) obtained by dividing the difference by the flange length L are calculated as the trajectory determination value, and the number of paths and the processing intermediate angle θn of each step are calculated, from a trajectory number determination map (see FIG. 8) in which the path number representing the number of times of bending to be bent in stages from the pre-processed angle θ₀ to the intended angle Ψ is determined in stages depending on the magnitude of the trajectory determination value, and from the calculated trajectory determination value.

Thus, it is possible to automatically and appropriately calculate the number of times of bending by reflecting the processing difficulty level on the basis of the difference between the pre-processed angle θ₀ and the intended angle Ψ.

Next, FIG. 10 which illustrates a case where the cross-sectional shape of the workpiece W is different in the movement direction of the processing roller 10 is a cross-sectional perspective view illustrating an example of a workpiece Wb (a workpiece W) having a different cross-sectional shape in the movement direction of the processing roller 10. FIG. 11 is a flowchart illustrating the flow of the movement control of the processing roller 10 when the cross-sectional shape of the workpiece W is different in the movement direction of the processing roller 10. FIG. 12 is a table illustrating a relation between the cross-section at a plurality of places acquired in the range in which the preliminary process is performed and the processing difficulty level. FIG. 13 is a diagram illustrating a trajectory number determination map which determines the number of paths of the processing roller 10 when the cross-sectional shape of the workpiece W is different in the movement direction of the processing roller 10.

The workpiece Wb illustrated in FIG. 10 is a portion on the rear side of the vehicle door, and the flange WF at the end portion of the workpiece W has a curved surface. The cross-sectional shape is different in the movement direction of the processing roller 10.

As illustrated in FIG. 11, a plurality (N pieces) of cross-sections having different positions in the movement direction are acquired, and each cross-section information is generated (S201). In the present embodiment, the cross-sectional shape is acquired at a predetermined interval, for example, on the order of several mm pitch, on the basis of preset data, such as design data which is set in the previous process. In the example illustrated in FIG. 12, 15 cross-sections are created. Further, as for how many cross-sections are created, it is possible to adopt an appropriate method, for example, such as a method for setting the cross-section on the basis of the range in which the preliminary process is performed or the shape of the cross-section.

Next, on the basis of the cross-section acquired in S201, the flange length L of each cross-section and the pre-processed angle θ₀ are acquired (S202). Next, values of (θ₀−Ψ)/L and (θ₀−Ψ) are calculated for each cross-section. In the example illustrated in FIG. 12, (θ₀−Ψ)/L and (θ₀−Ψ) are calculated for each of the 15 cross-sections.

The highest value (θ₀−Ψ)/L among the values (θ₀−Ψ)/L of each cross-section is acquired, and the highest value of θ₀−Ψ is acquired. In the example illustrated in FIG. 12, the highest value of (θ₀−Ψ)/L is 17.79, and the highest value of θ₀−Ψ is 62.61. The number of paths is determined in the same manner as in a case where the cross-sectional shape of the workpiece W is the same in the movement direction of the processing roller 10.

Also in this embodiment, as illustrated in the trajectory number determination map of FIG. 13, the range for determining the number of paths on the basis of the value of (θ₀−Ψ)/L is 1 path when the value of (θ₀−Ψ)/L is less than 7.0, the range is 2 paths when the value is 7.0 or more and less than 12.0, and the range is 3 paths when the value is 12.0 or more and less than 19.0. On the other hand, the range for determining the number of paths on the basis of the value of θ₀−Ψ is 1 path when the value of θ₀−Ψ is less than 10 deg, the range is 2 paths when the value is 10 deg or more and less than 60 degrees, and the range is 3 paths when the value is 60 deg or more and less than 110 deg. In the example illustrated in FIG. 12, since the highest value of (θ₀−Ψ)/L is 17.79, the range is 3 paths and since the highest value of θ₀−Ψ is 62.61 deg, the range is 3 paths.

The number of paths set on the basis of the highest value of (θ₀−Ψ)/L is compared with the number of paths set on the basis of the highest value of θ₀−Ψ, and the number of paths having the higher processing difficulty level is determined. In the example illustrated in FIG. 12, since the number of paths is 3 in each case, the number of paths is set to 3.

When the number of paths is determined in the process of S204, the process shifts to a process of calculating a processing intermediate angle (S205). In the present embodiment, also in the calculating of the processing intermediate angle in S205, as in the determination of the number of paths in S204, the highest value among the values of (θ₀−Ψ)/L is acquired, and the highest value among the values of θ₀−Ψ is acquired. The processing intermediate angle and the pushing amount in the subsequent processing are set for the highest value of (θ₀−Ψ)/L and the highest value of θ₀−Ψ.

A method for calculating the processing intermediate angle will be described. A processing intermediate angle θ1α is acquired on the basis of the number of paths determined by the value of (θ₀−Ψ)/L, and a processing intermediate angle θ1β is acquired on the basis of the number of paths determined by the value of (θ₀−Ψ). The processing intermediate angles θ1α and θ1β are obtained by dividing the angle, which is obtained by subtracting the intended angle Ψ from the pre-processed angle θ0, by the number of paths.

In the example of FIG. 12, No. 13 having the largest pre-processed angle is set as the pre-processed angle θn=92.61, and the intended angle Ψ=30 deg. In this case, as for (θ₀−Ψ)/L, the processing intermediate angles θ1α=71.74 deg, θ2α=50.87 deg, and θ3α=30 deg are set, and the number of paths is the same. Accordingly, as for θ₀−Ψ, the processing intermediate angles θ1β=71.74 deg, θ2β=50.87 deg, and θ3β=30 deg are set.

Further, the deviation of the value of (θ₀−Ψ)/L within the set range is calculated as a margin Mα. The margin Mα is a dimensionless number calculated with reference to an upper limit side of the setting range. The margin Mα is set, on the basis of the numerical value that determines the upper limit at which the number of paths in the setting range is determined, the highest numerical value of (θ₀−Ψ)/L, and the numerical value that determines a lower limit. The margin Mα indicates how far the numerical value for determining the number of paths is from the numerical value that determines the upper limit. In the above example, Mα=(19−17.79)/(19−12), and Mα=0.17 is set.

Similarly, the deviation of the value of θ₀−Ψ within the set range is calculated as a margin Mβ. The margin Mβ is calculated with reference to the upper limit side of the setting range. The margin Mβ is set, on the basis of the numerical value for determining the upper limit at which the number of paths in the setting range is determined, the highest numerical value of θ₀−Ψ, and the numerical value that determines the lower limit. The margin Mβ indicates how far the numerical value for determining the number of paths is from the numerical value that determines the upper limit. In the above example, Mβ=(110−61.92)/(110−60), and Mβ=0.95 is set.

A processing intermediate angle θn is calculated on the basis of the processing intermediate angle θ1α, the processing intermediate angle θ1β, the margin Mα, and the margin Mβ. As illustrated in FIG. 13, a processing intermediate angle is calculated by θn=1/(Mα+Mβ)×(Mβθnα+Mαθnβ) Formula 3. Further, in the example of FIG. 12, when applying θn=1/(Mα+Mβ)×(Mβθnα+Mαθn β) Formula 3, the processing intermediate angles θ1=71.74 deg, θ2=50.87 deg, and θ3=30 deg are set.

Next, an intermediate cross-section is created on the CAD on the basis of the largest angle θ0 among the respective cross-sections θ0 (S206). In the example of FIG. 12, θ0=92.61 deg is used. The pushing amount D1→n of the processing roller 10 is calculated on the basis of the intermediate section set in S206 (S207). The pushing amount D which is set for each path is set for each processing intermediate angle which is set in each path. Calculation of the pushing amount D is the same as in the above embodiment. In the example of FIG. 12, the pushing amount D1=2.9 mm is set in the first bending process, the pushing amount D2=4.3 mm is set in the second bending process, and the pushing amount D3=5.4 mm is set in the third bending process. Data drawn in each cross-section is output, and the flow ends (S208).

According to the bending method and the roller hemming apparatus 1 of the embodiment described above, the following effects are obtained. In a case where the shape of the workpiece Wb is different in the movement direction of the processing roller 10, in the trajectory determination step, the trajectory of the processing roller 10 is determined, on the basis of the pre-processed angle θ₀, the intended angle Ψ, and the flange length L of the first cross section of the flange WF viewed in the movement direction of the processing roller 10, and on the basis of the pre-processed angle θ₀, the intended angle Ψ, and the flange length L of a second cross section different from the first cross section of the flange WF viewed in the movement direction of the processing roller 10.

Thus, even when the cross-sectional shape is different, the trajectory of the processing roller 10 can be determined in consideration of the difference in shape.

Both the difference (θ₀−Ψ) between the pre-processed angle θ₀ of the first cross section and the intended angle Ψ, and the value ((θ₀−Ψ)/L) obtained by dividing the difference by the flange length L are calculated as the first trajectory determination value. Further, on the basis of both the difference (θ₀−Ψ) between the pre-processed angle θ₀ of the second cross section and the intended angle Ψ, and the value ((θ₀−Ψ)/L) obtained by dividing the difference by the flange length L, a second trajectory determination value is calculated. In other words, the number of paths and the bending angle of each step are calculated, from the trajectory number determination map (see FIG. 13) in which the path number representing the number of times of bending to be bent in stages from the pre-processed angle θ₀ to the intended angle Ψ is determined in stages depending on the magnitude of the trajectory determination value, and from the calculated first trajectory decision value and second trajectory decision value.

As a result, even when the cross section varies in the movement direction, the number of times of bending can be automatically and appropriately calculated by reflecting the processing difficulty level.

In the trajectory number determination map, values for determining the upper limit value (7.0 in 1 path, 12.0 in 2 paths, and 19.0 in 3 paths) are determined for each path, and the bending angle in each step is calculated by reflecting the margin Mα or the margin Mβ with respect to the upper limit value in the range (the range of 1 path, the range of 2 paths, or the range of 3 paths) to which the trajectory determination value plotted in the trajectory number determination map belongs.

As a result, it is possible to appropriately average the processing difficulty level in a case where the cross-sectional shape is different, and the bending process of the workpiece can be more stably performed.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments and can be appropriately modified. For example, the configuration is not limited to the shape of the processing roller of the above embodiment, and can be appropriately changed as long as it is possible to perform the bending process. Further, the trajectory number determination map is not limited to the one described in the above embodiment, and the trajectory number representing the number of times of bending to be bent in stages from the pre-processed angle to the intended angle may be in a table format determined in stages in accordance with the magnitude of the trajectory determination value. In this way, the trajectory number determination map can be appropriately changed depending on the circumstances.

EXPLANATION OF REFERENCE NUMERALS

-   1 roller hemming apparatus (workpiece bending apparatus) -   10 processing roller (processing tool) -   40 robot -   50 control unit -   W workpiece -   WF flange -   θ₀ pre-processed angle -   θn processing intermediate angle -   Ψ intended angle 

1. A workpiece bending method for performing a bending process on an end portion of a workpiece by a processing tool, the method comprising: a step of obtaining a pre-processed angle of the end portion before processing and an end portion length of a bent portion of the end portion; a trajectory determination step of determining a trajectory of the processing tool on the basis of the pre-processed angle, an intended angle after processing, and the end portion length; and a processing step of moving the processing tool in a predetermined direction on the basis of the trajectory determined in the trajectory determination step and bending the end portion up to the intended angle.
 2. The workpiece bending method according to claim 1, wherein, in the trajectory determination step, a difference between the pre-processed angle and the intended angle or a value obtained by dividing the difference by the end portion length or both are calculated as a trajectory determination value, and the number of times of bending and the bending angle of each step are calculated from a trajectory number determination map in which the trajectory number representing the number of times of bending to be bent in stages from the pre-processed angle to the intended angle is determined in stages depending on the magnitude of the trajectory determination value, and from the calculated trajectory determination value.
 3. The workpiece bending method according to claim 1, wherein when the shape of the end portion of the workpiece is different in the movement direction of the processing tool, in the trajectory determination step, the trajectory of the processing tool is determined on the basis of the pre-processed angle, the intended angle, and the end portion length of a first cross section of the end portion viewed in the movement direction of the processing tool, and on the basis of the pre-processed angle, the intended angle, and the end portion length of a second cross section different from the first cross section of the end portion viewed in the movement direction of the processing tool.
 4. The workpiece bending method according to claim 3, wherein a difference between the pre-processed angle and the intended angle of the first cross section, a value obtained by dividing the difference by the end portion length or both are calculated as a first trajectory determination value, a difference between the pre-processed angle and the intended angle of the second cross section, a value obtained by dividing the difference by the end portion length or both are calculated as a second trajectory determination value, and the number of times of bending and the bending angle of each step are calculated from a trajectory number determination map in which the trajectory number representing the number of times of bending to be bent in stages from the pre-processed angle to the intended angle is determined in stages depending on the magnitude of the trajectory determination value, and from the calculated first and second trajectory determination values.
 5. The workpiece bending method according to claim 4, wherein in the trajectory number determination map, values for determining an upper limit value for each trajectory number are determined, and the bending angle is calculated in each step by reflecting a deviation with respect to the upper limit value in the range to which the trajectory determination value plotted in the trajectory number determination map belongs.
 6. A workpiece bending apparatus which performs a bending process on an end portion of a workpiece by a processing tool, the apparatus comprising: a control unit which obtains a pre-processed angle of the end portion before processing and an end portion length of a bent portion of the end portion, and determines a trajectory of the processing tool on the basis of the pre-processed angle, an intended angle after processing, and the end portion length; and a robot which moves the processing tool in a predetermined direction on the basis of the trajectory determined in the control unit, and bends the end portion up to the intended angle.
 7. The workpiece bending apparatus according to claim 6, wherein the control unit calculates a difference between the pre-processed angle and the intended angle or a value obtained by dividing the difference by the end portion length or both, as a trajectory determination value, and the number of times of bending and the bending angle of each step are calculated, from a trajectory number determination map in which the trajectory number representing the number of times of bending to be bent in stages from the pre-processed angle to the intended angle is determined in stages depending on the magnitude of the trajectory determination value, and from the calculated trajectory determination value.
 8. The workpiece bending apparatus according to claim 6, wherein, when the shape of the end portion of the workpiece is different in the movement direction of the processing tool, the control unit determines the trajectory of the processing tool, on the basis of the pre-processed angle, the intended angle, and the end portion length of the first cross section of the end portion viewed in the movement direction of the processing tool, and on the basis of the pre-processed angle, the intended angle, and the end portion length of the second cross section different from the first cross section of the end portion viewed in the movement direction of the processing tool.
 9. The workpiece bending apparatus according to claim 8, wherein a difference between the pre-processed angle and the intended angle of the first cross section, a value obtained by dividing the difference by the end portion length or both are calculated as a first trajectory determination value, a difference between the pre-processed angle and the intended angle of the second cross section, a value obtained by dividing the difference by the end portion length or both are calculated as a second trajectory determination value, and the number of times of bending and the bending angle of each step are calculated, from a trajectory number determination map in which the trajectory number representing the number of times of bending to be bent in stages from the pre-processed angle to the intended angle is determined in stages depending on the magnitude of the trajectory determination value, and from the calculated first and second trajectory determination values.
 10. The workpiece bending apparatus according to claim 9, wherein in the trajectory number determination map, values for determining an upper limit value for each trajectory number are determined, and the bending angle is calculated in each step by reflecting a deviation with respect to the upper limit value in the range to which the trajectory determination value plotted in the trajectory number determination map belongs. 